Nylon composite material suitable for high-humidity environment and preparation method thereof

Abstract

The invention provides a nylon composite material suitable for a high-humidity environment and a preparation method of the nylon composite material, and belongs to the technical field of composite materials. Comprising the following components in parts by weight: 64-67 parts of nylon 6, 26-28 parts of glass fibers, 3-4 parts of nickel-doped silicon carbide fibers, 0.5-0.7 part of polyethylene glycol, 2-3 parts of a compatilizer, 0.2-0.5 part of an antioxidant and 0.2-0.5 part of a lubricant. The tensile property maintaining capability of the prepared composite material in a high-humidity environment can be well improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of composite materials, and in particular relates to a nylon composite material suitable for high-humidity environments and a preparation method thereof. Background Art

[0002] Nylon composites suitable for high-humidity environments are engineering plastics based on polyamide (PA) and reinforced with glass fiber (GF). For example, glass fiber is added to nylon 6 to create nylon composites suitable for high-humidity environments. The addition of glass fiber significantly improves the material's strength and rigidity. Glass fiber reinforcement also increases the heat distortion temperature, allowing the material to maintain structural stability even in high-temperature environments. These composites are widely used in the automotive, electrical, and power tool industries.

[0003] The nylon 6 matrix has a high water absorption rate, while glass fiber itself does not absorb water. The addition of glass fiber reduces the overall water absorption rate of the composite material due to the adjustment of the volume ratio, thereby improving the composite material's reliability in humid environments. However, the hygroscopicity of the nylon 6 matrix itself remains unchanged. When the composite material is used in high-humidity environments, moisture can still penetrate through the amide bonds of the nylon molecular chains, weakening the interfacial bonding between the glass fiber and PA6, reducing the tensile properties / tensile strength of the composite material, and weakening its load-bearing capacity. Summary of the Invention

[0004] In response to the above problems, the present invention proposes a nylon composite material suitable for high-humidity environments and a preparation method thereof, which greatly improves the ability of the composite material to maintain tensile properties in high-humidity environments.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] A nylon composite material suitable for high-humidity environments comprises the following components, calculated by weight: 64-67 parts of nylon 6, 26-28 parts of glass fiber, 3-4 parts of nickel-doped silicon carbide fiber, 0.5-0.7 parts of polyethylene glycol, 2-3 parts of a compatibilizer, 0.2-0.5 parts of an antioxidant, and 0.2-0.5 parts of a lubricant.

[0007] Preferably, the preparation method of the nickel-doped silicon carbide fiber is as follows: 95-100g of polycarbosilane is dissolved in 200-220mL of xylene, and then 2-2.5g of nano-nickel particles are added and ultrasonically dispersed to obtain a mixed solution; under vacuum conditions, the mixed solution is distilled to remove xylene to obtain nano-nickel-polycarbosilane; the nano-nickel-polycarbosilane is melt-spun, infusible treated and sintered to obtain nickel-doped silicon carbide fiber.

[0008] Preferably, the frequency of the ultrasonic dispersion is 30-40 kHz, and the time of the ultrasonic dispersion is 40-60 min.

[0009] Preferably, the temperature of the distillation treatment is 90-105° C., the time is 50-80 min, and the vacuum degree is -0.08 MPa.

[0010] Preferably, the melt spinning temperature is 280-320° C., the melt spinning pressure is 0.5-1.2 MPa, and the melt spinning speed is 0.5-2.0 mL / min.

[0011] Preferably, the infusibility treatment is performed at a constant temperature of 200-220°C.

[0012] Preferably, the specific operation of the sintering treatment is: in a nitrogen atmosphere, heating to 1200-1250°C at a rate of 5°C / min, keeping the temperature for 100-120 minutes, and then cooling to room temperature at a rate of 3-5°C / min.

[0013] Preferably, the compatibilizer includes any one of maleic anhydride grafted POE, maleic anhydride grafted polyethylene, and maleic anhydride grafted EPDM rubber, or a mixture of at least two thereof; the antioxidant includes antioxidant 245 and / or antioxidant 1010; and the lubricant is calcium stearate.

[0014] A method for preparing a nylon composite material suitable for a high-humidity environment comprises the following steps:

[0015] Step 1: adding nylon 6, glass fiber, nickel-doped silicon carbide fiber, polyethylene glycol, a compatibilizer, an antioxidant, and a lubricant into a high-pressure mixer and mixing to obtain a mixture;

[0016] Step 2: adding the mixture into a twin-screw extruder, melt-blending, and extruding into granules to obtain the nylon composite material suitable for high-humidity environments.

[0017] Preferably, the melt extrusion temperature of the twin-screw extruder is 220-270° C., and the screw speed is 210-320 r / min.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] The raw materials for preparing the nylon composite material suitable for high-humidity environments of the present invention include, in addition to the base material nylon 6 and the reinforcing material glass fiber, nickel-doped silicon carbide fiber and polyethylene glycol. The two can produce a synergistic effect in the glass fiber reinforced nylon 6 system, synergistically reduce the hygroscopicity of the prepared composite material, and further synergistically enhance the composite material's ability to maintain tensile properties in a high-humidity environment.

[0020] Specifically, on the one hand, in the preparation of nickel-doped silicon carbide fibers, nickel elements form active sites through surface doping, and form coordination bonds or covalent bonds with the terminal amino groups or carboxylic acid groups of nylon 6, thereby strengthening the interface bonding strength and reducing the water absorption channels caused by interface defects, thereby reducing the hygroscopicity of the composite material; polyethylene glycol reduces the agglomeration tendency of nickel-doped silicon carbide fibers through molecular chain entanglement and polar adsorption, improves the dispersion of nickel-doped silicon carbide fibers in the nylon 6 matrix, and effectively avoids local stress concentration and interface weakening caused by the agglomeration of nickel-doped silicon carbide fibers; the interface bonding of nickel-doped silicon carbide fibers and the dispersion improvement of polyethylene glycol synergistically reduce the interface water absorption channels, thereby synergistically reducing the hygroscopicity of the composite material.

[0021] On the other hand, the high roughness of the surface of nickel-doped silicon carbide fibers and the metallic properties of nickel can act as heterogeneous nucleating agents for nylon 6, promoting the formation of β-crystals. Although the water absorption rate of the β-crystal itself is higher than that of the α-crystal, polyethylene glycol and nickel-doped silicon carbide fibers synergistically induce nylon 6 to form a "dense β-crystal surface-tough amorphous inner layer" structure, utilizing the interfacial free volume difference and crystallization gradient construction between the crystalline and amorphous regions, and inhibiting / blocking the diffusion path of water molecules through physical barriers, thereby achieving the effect of synergistically reducing the hygroscopicity of the composite material and synergistically enhancing the composite material's ability to maintain tensile properties in a high-humidity environment. DETAILED DESCRIPTION

[0022] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0023] Example 1

[0024] A method for preparing a nylon composite material suitable for a high-humidity environment comprises the following steps:

[0025] Step 1: First, add 65 parts of nylon 6, 27 parts of glass fiber, and 3.5 parts of nickel-doped silicon carbide fiber into a high-pressure mixer and mix at 300 rpm for 1 minute; then add 0.6 parts of polyethylene glycol, 2.5 parts of a compatibilizer, 0.3 parts of an antioxidant, and 0.3 parts of a lubricant and mix at 450 rpm for 3 minutes to obtain a mixture.

[0026] Nylon 6 (Lanxess B30S food grade, Germany) was purchased from Shanghai Unos Plastic Technology Co., Ltd. The glass fiber was alkali-free glass fiber (3mm, Grade A) purchased from the Shuolong Mineral Products Processing Plant in Lingshou County. Polyethylene glycol (PEG-4000) was purchased from the Hai'an Petrochemical Plant in Jiangsu Province. The compatibilizer was maleic anhydride-grafted POE (Dow POE-g-MAH, USA) purchased from Dongguan Shangpin New Material Technology Co., Ltd. The antioxidant was antioxidant 1010 (premium grade) purchased from Dongguan Dinghai Plastic Chemical Co., Ltd. The lubricant was calcium stearate (premium grade) purchased from Dongguan Shanyi Plastic Co., Ltd.

[0027] Step 2: Set the melt extrusion temperature of the twin-screw extruder to 220-270° C. and the screw speed to 300 r / min, add the mixture into the twin-screw extruder, melt blend, and extrude into granules to obtain a nylon composite material suitable for high-humidity environments.

[0028] The specific setting temperatures of the nine zones of the twin-screw extruder from the feeding section to the die head are: 220℃, 230℃, 245℃, 260℃, 270℃, 270℃, 250℃, 230℃, and 220℃.

[0029] Nickel-doped silicon carbide fibers were prepared as follows: 98 g of polycarbosilane was dissolved in 210 mL of xylene, followed by the addition of 2.2 g of nano-nickel particles. The mixture was then dispersed by ultrasonication at 35 kHz for 50 minutes to obtain a mixture. The xylene was then removed by distillation at approximately 95°C under a vacuum of -0.08 MPa for 60 minutes to obtain the nano-nickel-polycarbosilane. The nano-nickel-polycarbosilane was first melt-spun at a temperature of approximately 310°C, a pressure of approximately 0.7 MPa, and a spinning speed of approximately 1.5 mL / min. The mixture was then infusible and placed in an air-circulating furnace with an oxygen concentration slightly above 20%. The oxygen content was monitored in real time to ensure crosslinking efficiency. The temperature was raised from room temperature to 210°C at a rate of 2°C / min to avoid sudden stress changes on the fiber surface that could lead to cracks. The mixture was then kept at this temperature for 3 hours to oxidize the fiber surface and form a cross-linked structure, preventing melt deformation during subsequent sintering. Then, the sintering process was continued. The nitrogen flow rate in the sintering furnace was maintained at about 8 L / min to ensure the timely discharge of pyrolysis by-products. Specifically, in a nitrogen (purity ≥ 99.999%) atmosphere, the temperature was raised to 1230°C at a rate of 5°C / min and kept at that temperature for 110 minutes to optimize the fiber structure. The fiber was then slowly cooled to room temperature at a rate of 4°C / min (staying at about 900°C for 10 minutes to relieve the crystal phase transition stress) to obtain nickel-doped silicon carbide fiber.

[0030] Polycarbosilane (molecular weight 1000-1800) was purchased from Forsman Technology (Beijing) Co., Ltd. Nano-nickel particles (purity ≥99.9, average particle size 50 nm) were purchased from Yunyan New Materials (Shanghai) Co., Ltd.

[0031] Example 2

[0032] The difference between this embodiment and embodiment 1 is that a method for preparing a nylon composite material suitable for a high-humidity environment comprises the following steps:

[0033] Step 1: First, add 64 parts of nylon 6, 26 parts of glass fiber, and 3 parts of nickel-doped silicon carbide fiber into a high-speed mixer and mix at 300 rpm for 1 minute; then add 0.5 parts of polyethylene glycol, 2 parts of a compatibilizer, 0.2 parts of an antioxidant, and 0.2 parts of a lubricant and mix at 450 rpm for 3 minutes to obtain a mixture.

[0034] Step 2: Set the melt extrusion temperature of the twin-screw extruder to 220-270° C. and the screw speed to 300 r / min, add the mixture into the twin-screw extruder, melt blend, and extrude into granules to obtain a nylon composite material suitable for high-humidity environments.

[0035] Example 3

[0036] The difference between this embodiment and embodiment 1 is that a method for preparing a nylon composite material suitable for a high-humidity environment comprises the following steps:

[0037] Step 1: First, add 67 parts of nylon 6, 28 parts of glass fiber, and 4 parts of nickel-doped silicon carbide fiber, by weight, into a high-speed mixer and mix at 300 rpm for 1 minute; then add 0.7 parts of polyethylene glycol, 3 parts of a compatibilizer, 0.5 parts of an antioxidant, and 0.5 parts of a lubricant, and mix at 450 rpm for 3 minutes to obtain a mixture.

[0038] Step 2: Set the melt extrusion temperature of the twin-screw extruder to 220-270° C. and the screw speed to 300 r / min, add the mixture into the twin-screw extruder, melt blend, and extrude into granules to obtain a nylon composite material suitable for high-humidity environments.

[0039] Comparative Example 1

[0040] The only difference between this comparative example and Example 1 is that the nickel-doped silicon carbide fiber is replaced by glass fiber and polyethylene glycol is deleted.

[0041] Specifically as follows: A method for preparing a nylon composite material suitable for a high humidity environment comprises the following steps:

[0042] Step 1: First, add 65 parts of nylon 6 and 30.5 parts of glass fiber into a high-speed mixer, and mix at 300 rpm for 1 minute; then add 2.5 parts of compatibilizer, 0.3 parts of antioxidant and 0.3 parts of lubricant, and mix at 450 rpm for 3 minutes to obtain a mixture.

[0043] Step 2: Set the melt extrusion temperature of the twin-screw extruder to 220-270° C. and the screw speed to 300 r / min, add the mixture into the twin-screw extruder, melt blend, and extrude into granules to obtain a nylon composite material suitable for high-humidity environments.

[0044] Comparative Example 2

[0045] The only difference between this comparative example and Example 1 is that the nickel-doped silicon carbide fiber is replaced by glass fiber.

[0046] Specifically as follows: A method for preparing a nylon composite material suitable for a high humidity environment comprises the following steps:

[0047] Step 1: First, add 65 parts of nylon 6 and 30.5 parts of glass fiber, by weight, into a high-speed mixer and mix at 300 rpm for 1 minute; then add 0.6 parts of polyethylene glycol, 2.5 parts of a compatibilizer, 0.3 parts of an antioxidant, and 0.3 parts of a lubricant, and mix at 450 rpm for 3 minutes to obtain a mixture.

[0048] Step 2: Set the melt extrusion temperature of the twin-screw extruder to 220-270° C. and the screw speed to 300 r / min, add the mixture into the twin-screw extruder, melt blend, and extrude into granules to obtain a nylon composite material suitable for high-humidity environments.

[0049] Comparative Example 3

[0050] The only difference between this comparative example and Example 1 is that polyethylene glycol is deleted.

[0051] Specifically as follows: A method for preparing a nylon composite material suitable for a high humidity environment comprises the following steps:

[0052] Step 1: First, add 65 parts of nylon 6, 27 parts of glass fiber, and 3.5 parts of nickel-doped silicon carbide fiber into a high-pressure mixer and mix at 300 rpm for 1 minute; then add 2.5 parts of a compatibilizer, 0.3 parts of an antioxidant, and 0.3 parts of a lubricant and mix at 450 rpm for 3 minutes to obtain a mixture.

[0053] Step 2: Set the melt extrusion temperature of the twin-screw extruder to 220-270° C. and the screw speed to 300 r / min, add the mixture into the twin-screw extruder, melt blend, and extrude into granules to obtain a nylon composite material suitable for high-humidity environments.

[0054] Test Example: ① Based on GB / T1040-92, the tensile strength σ0 of nylon composite material specimens suitable for high-humidity environments, prepared in Examples 1-3 and Comparative Examples 1-3, was measured. ② Each specimen was immersed in deionized water at 40±2°C for 48 hours, removed and air-dried, and the post-immersion tensile strength σ1 was measured. ③ The tensile strength loss rate, Rσ, was calculated using the formula: Rσ = (σ0 - σ1) / σ0 × 100%. A smaller Rσ value indicates a greater ability of the specimen to maintain tensile properties in high-humidity environments.

[0055] Test results: See Table 1.

[0056] Table 1. Test results statistics of test cases

[0057] Tensile strength σ0 (MPa) Tensile strength after immersion in water σ1 (MPa) Tensile strength loss rate Rσ (%) Example 1 187.5 180.4 3.8 Example 2 186.2 179.5 3.6 Example 3 187.9 180.6 3.9 Comparative Example 1 168.4 159.6 5.2 Comparative Example 2 166.7 154.9 7.1 Comparative Example 3 185.8 177.6 4.4

[0058] Analysis of Results: Analysis of Examples 1-3, combined with the data in Table 1, reveals that the tensile strength of the nylon composite material suitable for high-humidity environments produced by the present invention reached a high of 186.2 MPa or higher, and the tensile strength loss after immersion in deionized water at 40±2°C for 48 hours was as low as 3.9% or less. This demonstrates that the nylon composite material suitable for high-humidity environments produced by the present invention exhibits excellent tensile strength and excellent retention of tensile properties in high-humidity environments.

[0059] Example 1 and Comparative Examples 1 to 3 are analyzed in combination with the data in Table 1. By comparing Comparative Example 1 with Comparative Example 2, it can be seen that when the reinforcing material is a single glass fiber, the addition of polyethylene glycol will cause the nylon composite material suitable for high humidity environments to have a weakened ability to maintain tensile properties in high humidity environments.

[0060] This is because polyethylene glycol, as a polar substance, interferes with the regular arrangement of nylon 6 molecular chains, inhibits the formation of α-crystals, increases the proportion of amorphous regions in the composite material, increases the free volume of the molecular chains, and provides diffusion channels and adsorption sites for water molecules; and polyethylene glycol has limited compatibility with nylon 6 matrix and glass fiber, which can easily induce phase separation and form interfacial microcracks or pores, further expanding the water penetration path, thereby weakening the composite material's ability to maintain tensile properties in high-humidity environments.

[0061] By comparing Comparative Example 3 with Example 1, it can be seen that the introduction of nickel-doped silicon carbide fibers can enhance the ability of the nylon composite material suitable for high-humidity environments to maintain tensile properties in high-humidity environments; on this basis, the addition of polyethylene glycol can produce a synergistic effect and synergistically enhance the ability of the composite material to maintain tensile properties in high-humidity environments.

[0062] Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A nylon composite material suitable for high humidity environments, characterized by: The invention comprises the following components in parts by weight: 64-67 parts of nylon 6, 26-28 parts of glass fiber, 3-4 parts of nickel-doped silicon carbide fiber, 0.5-0.7 parts of polyethylene glycol, 2-3 parts of a compatibilizer, 0.2-0.5 parts of an antioxidant and 0.2-0.5 parts of a lubricant.

2. The nylon composite material suitable for high humidity environment according to claim 1, characterized in that: The preparation method of the nickel-doped silicon carbide fiber is as follows: 95-100g of polycarbosilane is dissolved in 200-220mL of xylene, and then 2-2.5g of nano-nickel particles are added and ultrasonically dispersed to obtain a mixed solution; the mixed solution is distilled under vacuum conditions to obtain nano-nickel-polycarbosilane; the nano-nickel-polycarbosilane is melt-spun, infusible, and sintered to obtain nickel-doped silicon carbide fiber.

3. The nylon composite material suitable for high humidity environment according to claim 2, characterized in that: The frequency of the ultrasonic dispersion is 30-40 kHz, and the time of the ultrasonic dispersion is 40-60 min.

4. The nylon composite material suitable for high humidity environment according to claim 2, characterized in that: The distillation treatment temperature is 90-105° C., the time is 50-80 min, and the vacuum degree is -0.08 MPa.

5. The nylon composite material suitable for high humidity environment according to claim 2, characterized in that: The melt spinning temperature is 280-320° C., the melt spinning pressure is 0.5-1.2 MPa, and the melt spinning speed is 0.5-2.0 mL / min.

6. The nylon composite material suitable for high humidity environment according to claim 2, characterized in that: The infusibility treatment is performed at a constant temperature of 200-220°C.

7. The nylon composite material suitable for high humidity environment according to claim 2, characterized in that: The specific operation of the sintering treatment is: in a nitrogen atmosphere, heating to 1200-1250°C at a rate of 5°C / min, keeping the temperature for 100-120 minutes, and then cooling to room temperature at a rate of 3-5°C / min.

8. The nylon composite material suitable for high humidity environment according to claim 1, characterized in that: The compatibilizer includes any one of maleic anhydride grafted POE, maleic anhydride grafted polyethylene, and maleic anhydride grafted EPDM rubber, or a mixture of at least two thereof; the antioxidant includes antioxidant 245 and / or antioxidant 1010; and the lubricant is calcium stearate.

9. A method for preparing a nylon composite material suitable for high humidity environments according to any one of claims 1 to 8, characterized in that: The following steps are involved: Step 1: adding nylon 6, glass fiber, nickel-doped silicon carbide fiber, polyethylene glycol, a compatibilizer, an antioxidant, and a lubricant into a high-pressure mixer and mixing to obtain a mixture; Step 2: adding the mixture into a twin-screw extruder, melt-blending, and extruding into granules to obtain the nylon composite material suitable for high-humidity environments.

10. The method for preparing a nylon composite material suitable for high humidity environments according to claim 9, characterized in that: The melt extrusion temperature of the twin-screw extruder is 220-270°C, and the screw speed is 210-320r / min.